At the time of marriage, a man accepted the following condition made by the woman: "If I take a second wife, then my wife will have the right to prono

Answer

This is termed Tafweedhut Talaaq. Tafweedhut Talaaq is the delegation by the husband of a Talaaq to his wife or to anyone else to issue Talaaq to his wife or she invokes Talaaq on herself if the husband commits a certain act which he promised not to do. In this case if the husband takes a second wife, the first wife has the right to pronounce Talaaq on herself and this will be one Talaaq Baa-in which ends the Nikah.